Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

155
FXUS63 KLOT 050458
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1058 PM CST Sun Jan 4 2026

.KEY MESSAGES...

- Above average temperatures in the 40s and 50s expected for the
  upcoming workweek.

- The potential for a period of fog and drizzle is increasing
  for Monday night into Tuesday.

- A late week system will bring showers to the area followed by
  falling temperatures and snow chances for the weekend.

&&

.DISCUSSION...
Issued at 300 PM CST Sun Jan 4 2026

While the potential was never all that high, based on latest
model guidance trends paired with the trajectory of upstream
observations and radar imagery suggesting precipitation will
remain north of the area, have opted to pull any remaining low
precipitation chances out of the forecast for far northern
Illinois. Still can`t fully rule out light mist sneaking down to
areas along the Wisconsin state line but no impacts are
expected.

Warm and moist air advection is still anticipated across the
region tonight into Monday with temperatures overnight holding
steady or only falling a few degrees overnight. The increased
low-level moisture may allow for some fog development into
Monday morning, currently favoring areas northwest of the
Chicago metro. Several of the available hi-res guidance then
have the fog and low-stratus redeveloping Monday night into
Tuesday. This could be paired with a period of rain and drizzle
as ascent increases through the low-cloud layer as another
disturbance drifts east across the region.

The aforementioned fog/drizzle could limit some of the warming
Monday and Tuesday with highs closer to the upper 30s or lower
40s, especially north of I-88, otherwise highs will be solidly
in the 40s across the remainder of the area, including the
potential for 50s toward central Illinois through the workweek.

There continue to be notable differences in the handling of the
late week system, with more northerly solutions (EPS) having
rain for the entire area and potentially thunderstorms, and
southerly solutions (GEFS) bringing snow accumulations across
northwest Illinois. Will continue to monitor trends to see if
they consolidate toward one solution or more of a blend of the
two. What is perhaps more certain is that in the wake of this
system, temperatures will fall back to more seasonable norms for
the weekend with highs in the 30s along with lingering snow
chances.

Petr

&&

.AVIATION /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 1058 PM CST Sun Jan 4 2026

Aviation forecast concerns for the 06Z TAFs:

- Marginal LLWS conditions into the predawn hours this morning.

- Development of low-MVFR or IFR ceilings later Monday
  morning/afternoon.

- Greater potential for IFR ceiling development Monday night,
  with drizzle and fog potential increasing late.

Surface low pressure was over south-central MN late this
evening, and will continue to track east-northeast across
central WI to northern LM by daybreak Monday. Surface pressure
falls have enhanced the low-level pressure gradient, resulting
in southerly winds occasionally gusting into to 20-25 kt range
across the terminals. A 45-50 kt west-southwest low level jet
at/above 2 kft AGL will linger across the area for the first few
hours of the forecast, though surface gustiness should limit the
magnitude of low-level shear. Winds will gradually ease and
turn southwest toward daybreak as the low pulls away from the
region. Winds will turn more westerly after daybreak as a
weakening cold front approaches the area. Winds will then
diminish and become southeast/east-southeast toward Monday
evening as weak surface high pressure drifts across the area.

Cloud-wise, a 10 kft mid-level VFR deck will be exiting the
region to the east at the start of the period, with VFR
conditions expected to persist into Monday morning. An area of
IFR/MVFR stratus along/west of the low track across MN and the
eastern Dakotas is forecast to shift east-southeast into the
area later Monday morning/midday however, and likely linger at
least though the afternoon. Some guidance indicates IFR CIGs
making it into northern IL with this, though favorable diurnal
timing suggests lower-end MVFR is more likely. It continues to
appear that there may be some improvement/scattering of this
stratus late afternoon/evening, especially farther east into the
Chicago terminals. KRFD, farther to the northwest has a lower
likelihood or at least a shorter duration of improvement into
early evening. MVFR/IFR probabilities then increase again into
the overnight hours of Monday night, as another disturbance
approaches and eventually leads to drizzle/fog and lowering cig
and vis conditions into Tuesday morning. IFR conditions appear
likely especially after midnight, with LIFR not out of the
question toward daybreak Tuesday.

Ratzer

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 5 AM CST Monday for the IL and IN
     nearshore waters.

&&

$$

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